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Fatty Pheromones

A new class of pheromones, triacylglycerides, helps male fruit flies mark their mates to deter rivals.

By | July 1, 2014

SCENT OF A MALE: A male fruit fly ignores a female (lower right) smeared with a male pheromone, and mates with an untreated female (left). NATIONAL UNIVERSITY OF SINGAPORE, JACQUELINE S.R. CHIN

EDITOR'S CHOICE IN BIOCHEMISTRY

The paper
J.S.R. Chin et al., “Sex-specific triacylglycerides are widely conserved in Drosophila and mediate mating behavior,” eLife, doi:10.7554/eLife.01751, 2014.

The suspicion
Animals often relay sexual messages through pheromones, typically small, volatile organic molecules. In recent years, Joanne Yew at the National University of Singapore and others had spotted triacylglycerides (TAGs)—compounds usually found in fatty tissue—on the exterior of fruit flies, a pattern hinting that they might be pheromones.

The scrutiny
In Yew’s latest study, her team found TAGs on a dozen desert-dwelling Drosophila species—including 13 different TAGs on two species alone—by using a mass spectrometer with a fine-point laser trained on the flies’ cuticle surface. “They’re secreted in just one region—the anogenital region—on males,” says Yew, and they increased in concentration as the flies reached sexual maturity.

The mating game
After observing that males snub freshly mated females—and finding TAGs on those females’ abdomens—Yew’s team dusted one of two females with TAGs and found that a male fly chose the untreated one, suggesting that the molecules act as pheromones. The researchers speculate that males mark females with TAGs when they mate, rendering them unattractive to subsequent suitors. “I’d like to know more details about how the triacylglycerides are doing what she’s saying they’re doing,” says geneticist Joel Levine of the University of Toronto, Mississauga. “How are they sensed by the male? How are they transmitted to the female?”  

The implication
TAGs are heavier than many known pheromones, suggesting that other pheromones may have been overlooked because of their size. “You’re missing a big piece of the puzzle if you’re not detecting these heavy chemicals,” Yew says.

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Avatar of: James V. Kohl

James V. Kohl

Posts: 152

July 1, 2014

Re: “How are they sensed by the male? How are they transmitted to the female?”

Sensing and signaling occur via conserved molecular mechanisms that link the epigenetic landscape to the physical landscape of DNA in the organized genomes of species from microbes to man.

Simply put Feedback loops link odor and pheromone signaling with reproduction

For a more technical representation see:

Nutrient-dependent pheromone-controlled ecological adaptations: from atoms to ecosystems

Abstract: "This atoms to ecosystems model of ecological adaptations links nutrient-dependent epigenetic effects on base pairs and amino acid substitutions to pheromone-controlled changes in the microRNA / messenger RNA balance and chromosomal rearrangements. The nutrient-dependent pheromone-controlled changes are required for the thermodynamic regulation of intracellular signaling, which enables biophysically constrained nutrient-dependent protein folding; experience-dependent receptor-mediated behaviors, and organism-level thermoregulation in ever-changing ecological niches and social niches. Nutrient-dependent pheromone-controlled ecological, social, neurogenic and socio-cognitive niche construction are manifested in increasing organismal complexity in species from microbes to man. Species diversity is a biologically-based nutrient-dependent morphological fact and species-specific pheromones control the physiology of reproduction. The reciprocal relationships of species-typical nutrient-dependent morphological and behavioral diversity are enabled by pheromone-controlled reproduction. Ecological variations and biophysically constrained natural selection of nutrients cause the behaviors that enable ecological adaptations. Species diversity is ecologically validated proof-of-concept. Ideas from population genetics, which exclude ecological factors, are integrated with an experimental evidence-based approach that establishes what is currently known. This is known: Olfactory/pheromonal input links food odors and social odors from the epigenetic landscape to the physical landscape of DNA in the organized genomes of species from microbes to man during their development."

Avatar of: James V. Kohl

James V. Kohl

Posts: 152

July 2, 2014

Journal article abstract excerpt: "The diversification of chemical cues used by desert-adapted Drosophila as pheromones may be related to their specialized diet of fermenting cacti."

No attempt is made to link the specialized diet from ecological variation to amino acid substitutions that differentiate cell types, which are manifested in the morphological and behavioral phenotypes of organisms from microbes to man. However, fermentation links nutrient uptake and the metabolism of nutrients to species-specific pheromones and controlled ecological adaptations of all species.

For example, fermented milk products and increased vitamin D appear to have led to the vitamin-dependent genomic stability of human populations in which nutrient-dependent lactose persistence led to the advent of the hemoglobin S variant.

Although the variant is considered to be a mutation by evolutionary theorists, it is one of more than 1100 hemoglobin variants that have clearly stabilized the human genome in different populations via the conserved molecular mechanisms of ecological adaptations that result in hemoglobin variants in other species (e.g., deer mice,hummingbirds, etc).

Dobzhansky (1973)noted that hemoglobin variants attributed to one amino acid substitution differentiate the cell types of gorillas, chimpanzees, and modern humans. However, I think he may already have offended theorists at the time he first mentioned a hemoglobin variant.

In Biology, molecular and organismic (1964), he wrote: "The notion has gained some currency that the only worthwhile biology is molecular biology. All else is "bird watching" or "butterfly collecting." Bird watching and butterfly collecting are occupations manifestly unworthy of serious scientists!" p. 443

Until the theorists get over the insult and proceed to learn about the conserved molecular mechanisms of cell type differentiation that link species from microbes to man, we may continue to see disparate thoughts about cause and effect instead of models of biodiversity based on ecological variation that leads to ecological adaptations.

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